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Carbon monoxide ( CO) is a colorless, odorless, tasteless, and poisonous gas. The most
commonly occurring global air pollutant, CO is produced by the incomplete burning of
carbon- containing fuels.
Sources
The major natural source of atmospheric CO is from the decomposition of organic matter.
The major man- made source is motor vehicle exhaust, which can account for more than 90
percent of all CO in large urban areas. Secondary sources include industrial processes and
solid waste incineration. Although the EPA has measured an overall downward trend in CO
concentrations throughout the United States, several large urban areas ( outside of North
Carolina) are still experiencing high levels of CO.
Effects
CO binds to blood hemoglobin more readily than does oxygen. CO inhalation reduces the
ability of the blood to carry oxygen, causing harm to the cardiovascular and nervous systems.
Individuals with anemia and heart and lung diseases are particularly sensitive to elevated
CO levels. Low concentrations can impair thinking, vision and alertness. High
concentrations can increase fatigue, cause dizziness and headaches, reduce work capacity,
and harm fetal development.
Although elevated levels of CO do not directly harm the environment, CO blocks the
removal of the greenhouse gases blamed for global climate warming. CO removes hydroxyl
radicals in the atmosphere; these hydroxyl radicals help lower the concentration of many
greenhouse gases, especially methane.
Trends
Carbon monoxide levels have declined steadily in North Carolina, dropping about 20
percent from 1972 to 1995 ( Figure 6, Figure 7). Although North Carolina exceeded the 8-
hour standard for CO many times before 1987, no exceedances have occurred since 1990
( Figure 8). There has never been an exceedance of the 1- hour standard in North Carolina.
The decline in CO concentrations is primarily due to stricter controls on automobile exhaust,
leading to A cleaner @ cars. This drop is remarkable because it occurred while population was
growing rapidly in North Carolina, causing more traffic and urban sprawl.

13
Carbon monoxide ( CO) is a colorless, odorless, tasteless, and poisonous gas. The most
commonly occurring global air pollutant, CO is produced by the incomplete burning of
carbon- containing fuels.
Sources
The major natural source of atmospheric CO is from the decomposition of organic matter.
The major man- made source is motor vehicle exhaust, which can account for more than 90
percent of all CO in large urban areas. Secondary sources include industrial processes and
solid waste incineration. Although the EPA has measured an overall downward trend in CO
concentrations throughout the United States, several large urban areas ( outside of North
Carolina) are still experiencing high levels of CO.
Effects
CO binds to blood hemoglobin more readily than does oxygen. CO inhalation reduces the
ability of the blood to carry oxygen, causing harm to the cardiovascular and nervous systems.
Individuals with anemia and heart and lung diseases are particularly sensitive to elevated
CO levels. Low concentrations can impair thinking, vision and alertness. High
concentrations can increase fatigue, cause dizziness and headaches, reduce work capacity,
and harm fetal development.
Although elevated levels of CO do not directly harm the environment, CO blocks the
removal of the greenhouse gases blamed for global climate warming. CO removes hydroxyl
radicals in the atmosphere; these hydroxyl radicals help lower the concentration of many
greenhouse gases, especially methane.
Trends
Carbon monoxide levels have declined steadily in North Carolina, dropping about 20
percent from 1972 to 1995 ( Figure 6, Figure 7). Although North Carolina exceeded the 8-
hour standard for CO many times before 1987, no exceedances have occurred since 1990
( Figure 8). There has never been an exceedance of the 1- hour standard in North Carolina.
The decline in CO concentrations is primarily due to stricter controls on automobile exhaust,
leading to A cleaner @ cars. This drop is remarkable because it occurred while population was
growing rapidly in North Carolina, causing more traffic and urban sprawl.